Re: Local 'languages'
"Genuine question - what is the difference between a dialect and a language?"
This is one of those questions which doesn't have a very good answer anymore.
Originally, it was mostly about writing - Language has a standardized written form and dialect is just the crazy things poor people say when the fail miserably to replicate it in sound form. This was considered a pretty good definition back in the early 1700s when linguistics was just starting out as a discipline and 'civilisation' was considered to stretch from roughly the mouth of the Danube to the Welsh border, and there didn't seem much point in leaving it's boundaries to study what people outside them were doing. The rest of the world was, after all, full of weirdos who couldn't speak proper languages anyway.
However, paradigms change, and it was eventually pointed out that there's loads of people who don't actually use writing who are, none the less, using distinct languages. Like, everyone alive prior to about 3000BC, for starters, along with most people prior to 1800 and a fair number still around today. At that point, though, the classification had become too useful to dispose of, despite the fact that the original definition of their difference was now recognized to be bollocks. So linguists started having to come up with increasingly complex justifications for the categories to exist because they were conceptually too handy to get rid of. It's now hard to find a meaningful explanation of the different that doesn't involve at least some kind of chart, and usually 2 or 3 with multi-page explanations.
There's a lot of this in social sciences. Anthropology has a similar problem with 'race', which was so embedded in the literature when people started questioning the concept's definition (turns out it hasn't actually got one; no-one noticed this for the first hundred years or so of using it) that it's now very hard to get rid of it. But even harder sciences like Biology have issues with it tho - a lot of the classification work in Linnaeus's taxonomy turns out to not really make a lot of sense once you have a better understanding of biology than you could get from a 2-week course in the early 1700s, and the whole thing had to be hastily retro-fitted to follow the phylogeny of organisms after Darwin. There's at least a couple of radical modern biologists who have started to question whether even the idea of species is actually a useful way of categorizing life.